This invention relates to charged particle energy analysers and in particular to charged particle microscopes, including spectromicroscopes. More particularly, the invention relates to charged particle energy analysers for investigating a selected area of the surface of a specimen.
It is known for example from GB-A-No. 1,367,302 to provide a charged particle energy analyser for investigating a selected area of the surface of a specimen comprising a specimen holder, a source of radiation arranged to direct radiation on to an external surface of a specimen on the holder and to cause charged particles to be emitted therefrom, a magnetic lens so disposed that the specimen holder lies within and on the axis of the magnetic imaging field of the lens and particles emitted from the specimen are brought to a focus by the field, a diaphragm containing a collection aperture disposed on the axis of the field to define the collection angle of the lens and analysing means for analysing the energy of the charged particles collected from the specimen and received by said analysing means.
In the analyser of GB-A-No. 1,367,302 the selected area of the specimen from which the analysing means receives charged particles is the whole area of the specimen on the axis from which the collection aperature receives charged particles. This however, does not enable the operator to examine charged particles received from only a very small selected area of the specimen, for example of the order of 10-50 microns diameter, rather than of about 250 microns diameter as in current practice.